From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions When using eBPF to probe CS CALL instructions within a function, a crash can be triggered. The eBPF tool probes offset 257 of the __hrtimer_run_queues() function: <__hrtimer_run_queues+249>: nopl 0x0(%rax,%rax,1) <__hrtimer_run_queues+254>: mov %r14,%rdi <__hrtimer_run_queues+257>: cs call <__x86_indirect_thunk_r12> <__hrtimer_run_queues+263>: mov %eax,%r12d <__hrtimer_run_queues+266>: xchg %ax,%ax <__hrtimer_run_queues+268>: mov %r13,%rdi Which triggers this crash: BUG: unable to handle page fault for address: 00000000000f41c9 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P RIP: 0010:__hrtimer_run_queues+0x106/0x230 Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is at the 6th byte of the above CS CALL instruction. Since the CS CALL instruction occupies 6 bytes, the exception occurred in the middle of that call instruction. The root cause is that when using eBPF tools to probe in the middle of a function, a kprobe with INT3 is used as the underlying implementation. During single-step emulation of the original CALL instruction, int3_emulate_call() assumes that the probed CALL instruction is 5 bytes long. However, the actual CS-prefixed CALL instruction occupies 6 bytes, so it constructs an incorrect exception return address. When the CPU returns from the kprobe handler, the next instruction to be executed is at the address of the last byte of that CS CALL instruction. Coincidentally, starting from that address, the CPU fetches and decodes a completely different instruction, which ultimately triggers a kernel crash. Fix the issue by using the actual instruction length obtained from the instruction decoder when constructing the exception return address, rather than relying on the hardcoded CALL_INSN_SIZE macro. [ mingo: Refined the changelog ] Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step") Suggested-by: Masami Hiramatsu (Google) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- drivers/gnss/usb.c | 214 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 214 insertions(+) create mode 100644 drivers/gnss/usb.c (limited to 'drivers/gnss/usb.c') diff --git a/drivers/gnss/usb.c b/drivers/gnss/usb.c new file mode 100644 index 000000000..0d9dde023 --- /dev/null +++ b/drivers/gnss/usb.c @@ -0,0 +1,214 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Generic USB GNSS receiver driver + * + * Copyright (C) 2021 Johan Hovold + */ + +#include +#include +#include +#include +#include +#include +#include + +#define GNSS_USB_READ_BUF_LEN 512 +#define GNSS_USB_WRITE_TIMEOUT 1000 + +static const struct usb_device_id gnss_usb_id_table[] = { + { USB_DEVICE(0x1199, 0xb000) }, /* Sierra Wireless XM1210 */ + { } +}; +MODULE_DEVICE_TABLE(usb, gnss_usb_id_table); + +struct gnss_usb { + struct usb_device *udev; + struct usb_interface *intf; + struct gnss_device *gdev; + struct urb *read_urb; + unsigned int write_pipe; +}; + +static void gnss_usb_rx_complete(struct urb *urb) +{ + struct gnss_usb *gusb = urb->context; + struct gnss_device *gdev = gusb->gdev; + int status = urb->status; + int len; + int ret; + + switch (status) { + case 0: + break; + case -ENOENT: + case -ECONNRESET: + case -ESHUTDOWN: + dev_dbg(&gdev->dev, "urb stopped: %d\n", status); + return; + case -EPIPE: + dev_err(&gdev->dev, "urb stopped: %d\n", status); + return; + default: + dev_dbg(&gdev->dev, "nonzero urb status: %d\n", status); + goto resubmit; + } + + len = urb->actual_length; + if (len == 0) + goto resubmit; + + ret = gnss_insert_raw(gdev, urb->transfer_buffer, len); + if (ret < len) + dev_dbg(&gdev->dev, "dropped %d bytes\n", len - ret); +resubmit: + ret = usb_submit_urb(urb, GFP_ATOMIC); + if (ret && ret != -EPERM && ret != -ENODEV) + dev_err(&gdev->dev, "failed to resubmit urb: %d\n", ret); +} + +static int gnss_usb_open(struct gnss_device *gdev) +{ + struct gnss_usb *gusb = gnss_get_drvdata(gdev); + int ret; + + ret = usb_submit_urb(gusb->read_urb, GFP_KERNEL); + if (ret) { + if (ret != -EPERM && ret != -ENODEV) + dev_err(&gdev->dev, "failed to submit urb: %d\n", ret); + return ret; + } + + return 0; +} + +static void gnss_usb_close(struct gnss_device *gdev) +{ + struct gnss_usb *gusb = gnss_get_drvdata(gdev); + + usb_kill_urb(gusb->read_urb); +} + +static int gnss_usb_write_raw(struct gnss_device *gdev, + const unsigned char *buf, size_t count) +{ + struct gnss_usb *gusb = gnss_get_drvdata(gdev); + void *tbuf; + int ret; + + tbuf = kmemdup(buf, count, GFP_KERNEL); + if (!tbuf) + return -ENOMEM; + + ret = usb_bulk_msg(gusb->udev, gusb->write_pipe, tbuf, count, NULL, + GNSS_USB_WRITE_TIMEOUT); + kfree(tbuf); + if (ret) + return ret; + + return count; +} + +static const struct gnss_operations gnss_usb_gnss_ops = { + .open = gnss_usb_open, + .close = gnss_usb_close, + .write_raw = gnss_usb_write_raw, +}; + +static int gnss_usb_probe(struct usb_interface *intf, const struct usb_device_id *id) +{ + struct usb_device *udev = interface_to_usbdev(intf); + struct usb_endpoint_descriptor *in, *out; + struct gnss_device *gdev; + struct gnss_usb *gusb; + struct urb *urb; + size_t buf_len; + void *buf; + int ret; + + ret = usb_find_common_endpoints(intf->cur_altsetting, &in, &out, NULL, + NULL); + if (ret) + return ret; + + gusb = kzalloc_obj(*gusb); + if (!gusb) + return -ENOMEM; + + gdev = gnss_allocate_device(&intf->dev); + if (!gdev) { + ret = -ENOMEM; + goto err_free_gusb; + } + + gdev->ops = &gnss_usb_gnss_ops; + gdev->type = GNSS_TYPE_NMEA; + gnss_set_drvdata(gdev, gusb); + + urb = usb_alloc_urb(0, GFP_KERNEL); + if (!urb) { + ret = -ENOMEM; + goto err_put_gdev; + } + + buf_len = max(usb_endpoint_maxp(in), GNSS_USB_READ_BUF_LEN); + + buf = kzalloc(buf_len, GFP_KERNEL); + if (!buf) { + ret = -ENOMEM; + goto err_free_urb; + } + + usb_fill_bulk_urb(urb, udev, + usb_rcvbulkpipe(udev, usb_endpoint_num(in)), + buf, buf_len, gnss_usb_rx_complete, gusb); + + gusb->intf = intf; + gusb->udev = udev; + gusb->gdev = gdev; + gusb->read_urb = urb; + gusb->write_pipe = usb_sndbulkpipe(udev, usb_endpoint_num(out)); + + ret = gnss_register_device(gdev); + if (ret) + goto err_free_buf; + + usb_set_intfdata(intf, gusb); + + return 0; + +err_free_buf: + kfree(buf); +err_free_urb: + usb_free_urb(urb); +err_put_gdev: + gnss_put_device(gdev); +err_free_gusb: + kfree(gusb); + + return ret; +} + +static void gnss_usb_disconnect(struct usb_interface *intf) +{ + struct gnss_usb *gusb = usb_get_intfdata(intf); + + gnss_deregister_device(gusb->gdev); + + kfree(gusb->read_urb->transfer_buffer); + usb_free_urb(gusb->read_urb); + gnss_put_device(gusb->gdev); + kfree(gusb); +} + +static struct usb_driver gnss_usb_driver = { + .name = "gnss-usb", + .probe = gnss_usb_probe, + .disconnect = gnss_usb_disconnect, + .id_table = gnss_usb_id_table, +}; +module_usb_driver(gnss_usb_driver); + +MODULE_AUTHOR("Johan Hovold "); +MODULE_DESCRIPTION("Generic USB GNSS receiver driver"); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1